Muscular Efficiency Research Articles

Leg cycling efficiency is unaltered in healthy aging regardless of sex or training status.

Muscular efficiency during exercise has been used to interrogate aspects of human muscle energetics, including mitochondrial coupling and biomechanical efficiencies. Typically, assessments of muscular efficiency have involved graded exercises. Results of previous studies have been interpreted to indicate a decline in exercise efficiency with aging owing to decreased mitochondrial function. However, discrepancies in variables such as exercise stage duration, cycling cadence, and treadmill walking mechanics may have affected interpretations of results. Furthermore, recent data from our lab examining the ATP to oxygen ratio (P:O) in mitochondrial preparations isolated from NIA mouse skeletal muscle showed no change with aging. Thus, we hypothesized that delta efficiency (Δ€) during steady-rate cycling exercise would not be altered in older healthy subjects compared with young counterparts regardless of biological sex or training status. Young (21-35 yr) and older (60-80 yr) men (n = 21) and women (n = 20) underwent continual, progressive leg cycle ergometer tests pedaling at 60 RPM for three stages (35, 60, 85 W) lasting 4 min. Δ€was calculated as: (Δ work accomplished/Δ energy expended). Overall, cycling efficiencies were not significantly different in older compared with young subjects. Similarly, trained subjects did not exhibit significantly different exercise efficiencies compared to untrained. Moreover, there were no differences between men and women. Hence, our results obtained on healthy young and older subjects are interpreted to mean that previous reports of decreased efficiency in older individuals were attributable to metabolic or biomechanical comorbidities, not aging per se.NEW & NOTEWORTHY Muscular power is reduced, but the efficiency of movement is unaltered in healthy aging.

Muscle Fat and Volume Differences in People With Hip-Related Pain Compared With Controls: A Machine Learning Approach.

Hip-related pain (HRP) affects young to middle-aged active adults and impacts physical activity, finances and quality of life. HRP includes conditions like femoroacetabular impingement syndrome and labral tears. Lateral hip muscle dysfunction and atrophy in HRP are more pronounced in advanced hip pathology, with limited evidence in younger populations. While MRI use for assessing hip muscle morphology is increasing, with automated deep-learning techniques showing promise, studies assessing their accuracy are limited. Therefore, we aimed to compare hip intramuscular fat infiltrate (MFI) and muscle volume, in individuals with and without HRP as well as assess the reliability and accuracy of automated machine-learning segmentations compared with human-generated segmentation. This cross-sectional study included sub-elite/amateur football players (Australian football and soccer) with a greater than 6-month history of HRP [n = 180, average age 28.32, (standard deviation 5.88) years, 19% female] and a control group of sub-elite/amateur football players without pain [n = 48, 28.89 (6.22) years, 29% female]. Muscle volume and MFI of gluteus maximus, medius, minimis and tensor fascia latae were assessed using MRI. Associations between muscle volume and group were explored using linear regression models, controlling for body mass index, age, sport and sex. A convolutional neural network (CNN) machine-learning approach was compared with human-performed muscle segmentations in a subset of participants (n = 52) using intraclass correlation coefficients and Sorensen-Dice index. When considering adjusted estimates of muscle volume, there were significant differences observed between groups for gluteus medius (adjusted mean difference 23 858 mm3 [95% confidence interval 7563, 40 137]; p = 0.004) and tensor fascia latae (6660 mm3 [2440, 13 075]; p = 0.042). No differences were observed between groups for gluteus maximus (18 265 mm3 [-21 209, 50 782]; p = 0.419) or minimus (3893 mm3 [-2209, 9996]; p = 0.21). The CNN was trained for 30 000 iterations and assessed its accuracy and reliability on an independent testing dataset, achieving high segmentation accuracy (mean Sorenson-Dice index >0.900) and excellent muscle volume and MFI reliability (ICC2,1 > 0.900). The CNN outperformed manual raters, who had slightly lower interrater accuracy (Sorensen-Dice index >0.800) and reliability (ICC2,1 > 0.800). The increased muscle volumes in the symptomatic group compared with controls could be associated with increased myofibrillar size, sarcoplasmic hypertrophy or both. These changes may facilitate greater muscular efficiency for a given load, enabling the athlete to maintain their normal level of function. In addition, the CNNs for muscle segmentation was more efficient and demonstrated excellent reliability in comparison to manual segmentations.

595-P: Exercise Training Improves Cardiorespiratory Parameters but Not VO2peak in People with Type 2 Diabetes

Maximal oxygen consumption (VO2peak), a measure of cardiorespiratory fitness (CRF), is a strong predictor of mortality. People with type 2 diabetes (T2D) have lower VO2peak compared to healthy controls, and unfortunately, studies suggest that training has limited effects to improve VO2peak in T2D. Although VO2peak is a key component, additional respiratory functions may also be important markers of cardio-metabolic fitness. Here, we determined the effects of a 10-week moderate-intensity exercise training program on VO2peak, power (indicator of muscle strength), VO2/work (index of the body’s efficiency at producing work), OUES (protective in heart failure), and ventilatory threshold (marker of aerobic endurance) in lean, obese, and T2D subjects. Training improved VO2peak in lean and obese, but not in T2D (Table 1). Likewise, training increased power, and tended to increase OUES in lean and obese, but not T2D. However, training was effective in increasing ventilatory threshold (VT) and VO2/Work in T2D, and also improved glycemic control (HbA1c). We hypothesize that the increased VT functions to improve training-induced muscular efficiency and capillary delivery, contributing to improved glycemic control. In conclusion, despite no change in VO2peak, exercise training increases multiple CRF and metabolic parameters in people with T2D, and should continue to be a mainstay in treatment of T2D. Disclosure R.Middelbeek: Research Support; Novo Nordisk. L.Simpson: None. G.A.Hansbury: None. N.P.Carbone: None. P.Nigro: None. S.J.Lessard: None. M.Vamvini: None. L.Goodyear: None. Funding National Institutes of Health (K23DK114550 to R.M.), (R01DK112283 to L.G.); Joslin Diabetes Center (T32DK07260-038, 5P30DK36836)

Fitness and metabolic response to exercise in young adult survivors of childhood lymphoma.

Childhood lymphoma survivors (CLSs) are at high risk of reduced daily activity. This work studied metabolic substrate use and cardiorespiratory function in response to exercise in CLSs. Twenty CLSs and 20 healthy adult controls matched for sex, age, and BMI took an incremental submaximal exercise test to determine fat/carbohydrate oxidation rates. Resting echocardiography and pulmonary functional tests were performed. Physical activity level, and blood metabolic and hormonal levels were measured. CLSs reported more physical activity than controls (6317 ± 3815 vs. 4268 ± 4354 MET-minutes/week, p = 0.013), had higher resting heart rate (83 ± 14 vs. 71 ± 13bpm, p = 0.006), and showed altered global longitudinal strain (- 17.5 ± 2.1 vs. - 19.8 ± 1.6%, p = 0.003). We observed no difference in maximal fat oxidation between the groups, but it was reached at lower relative exercise intensities in CLSs (Fatmax 17.4 ± 6.0 vs. 20.1 ± 4.1mL/kg, p = 0.021). At V̇O2 peak, CLSs developed lower relative exercise power (3.2 ± 0.9 vs. 4.0 ± 0.7 W/kg, p = 0.012). CLSs reported higher levels of physical activity but they attained maximal fat oxidation at lower relative oxygen uptake and applied lower relative power at V̇O2peak. CLSs may thus have lower muscular efficiency, causing greater fatigability in response to exercise, possibly related to chemotherapy exposure during adolescence and childhood. Long-term follow-up is essential and regular physical activity needs to be sustained.

Mechanical and Morphological Changes of the Plantar Flexor Musculotendinous Unit in Children with Unilateral Cerebral Palsy Following 12 Weeks of Plyometric Exercise: A Randomized Controlled Trial.

To investigate how plyometric exercise (PLYO-Ex) affects mechanics and morphometrics of the plantar flexor musculotendinous unit in children with unilateral cerebral palsy, 38 participants (aged 10-16 years) were allocated at random to either the PLYO-Ex group (n = 19; received 24 sessions of plyometric muscle loading, conducted 2 times a week for 3 months in succession) or the control group (n = 19; underwent traditional physical therapy for the same frequency and duration). Measurements were taken pre- and post-intervention. Standard ultrasound imaging was applied to evaluate morphometrics of the gastrocnemius muscle and Achilles tendon unit and an isokinetic dynamometer was used to evaluate maximum voluntary isometric plantar flexors contraction (IVCmax). With controlling for pre-treatment values, significant post-treatment changes favoring the PLYO-Ex group were observed for morphological (tendon (p = 0.003, η2p = 0.23) length; belly length (p = 0.001, η2p = 0.27); tendon thickness (p = 0.035, η2p = 0.35); muscle thickness (p = 0.013, η2p = 0.17); fascicle length (p = 0.009, η2p = 0.18); pennation angle (p = 0.015, η2p = 0.16)) and mechanical and material properties (IVCmax (p = 0.009, η2p = 0.18); tendon's elongation (p = 0.012, η2p = 0.17), stiffness (p = 0.027, η2p = 0.13); stress (p = 0.006, η2p = 0.20); strain (p = 0.004, η2p = 0.21)). In conclusion, plyometric exercise induces significant adaptations within the musculotendinous unit of the plantar flexors in children with unilateral cerebral palsy. These adaptations could improve muscular efficiency and consequently optimize physical/functional performance.

Efficiency of cycling exercise: Quantification, mechanisms, and misunderstandings.

The energetics of cycling represents a well-studied area of exercise science, yet there are still many questions that remain. Efficiency, broadly defined as the ratio of energy output to energy input, is one key metric that, despite its importance from both a scientific as well as performance perspective, is commonly misunderstood. There are many factors that may affect cycling efficiency, both intrinsic (e.g., muscle fiber type composition) and extrinsic (e.g., cycling cadence, prior exercise, and training), creating a complex interplay of many components. Due to its relative simplicity, the measurement of oxygen uptake continues to be the most common means of measuring the energy cost of exercise (and thus efficiency); however, it is limited to only a small proportion of the range of outputs humans are capable of, further limiting our understanding of the energetics of high-intensity exercise and any mechanistic bases therein. This review presents evidence that delta efficiency does not represent muscular efficiency and challenges the notion that the slow component of oxygen uptake represents decreasing efficiency. It is noted that gross efficiency increases as intensity of exercise increases in spite of the fact that fast-twitch fibers are recruited to achieve this high power output. Understanding the energetics of high-intensity exercise will require critical evaluation of the available data.

The effect of two different types of removable partial dentures on chewing activity and muscle efficiency.

Background and objectives: Cobalt chromium removable partial denture has been in use for years and despite of the advantages that cobalt chromium provides, it has many disad‐ vantages. In the recent years flexible removable partial denture has been introduced to dentistry with many advantages over cobalt chromium removable partial denture . The purpose of this study was to evaluate the effect of cobalt chromium and flexible removable partial denture on chewing activity and muscle efficiency. Methods: Ten patients were selected, all of them had completely edentulous maxilla and Kennedy Class I partially edentulous lower arch. eight male and two females with their ages ranging from 45 to 60 years. For each patient, an upper complete denture and two lower removable partial dentures (cobalt chromium and flexible) were constructed. Once the dentures were completed, muscle efficiency with the use of Electromyography and chew‐ ing activity by sieving method was performed in scheduled visits. Statistical analysis of data was achieved by means of (SPSS 25). And performing (independent sample T test, one‐way anova test, and multiple comparison Tukey test). Results: The chewing activity test, revealed a statistically significant difference (P< 0.05) between first and fourth visit concerning the flexible partial denture and improvement of chewing, for the cobalt chromium removable partial denture although there was improve‐ ment of chewing but it was not significant. Regarding the muscle efficiency test, this test revealed that there was no major significance between flexible and cobalt chromium re‐ movable partial denture and they are almost the same, but we can notice improvements of muscular efficiency specially in masseter muscle. Conclusions: Within the limitations of this study, it has been concluded that the muscle efficiency is improved within one month of insertion of both types of removable partial denture . Both flexible and cobalt chromium dentures increased muscle efficiency. Flexible removable partial denture increased chewing activity slightly better than cobalt chromium, while cobalt chromium was marginally better at chewing of hard food comparing to flexible denture.

Maximum Voluntary Molar and Incisor Biting Force and Morphological Variables in Subjects With Different Vertical Skeletal Patterns

Objective: To estimate the maximum voluntary molar biting force (MBF) and incisor biting force (IBF) and their relationship to morphological variables in subjects with different vertical skeletal patterns. Materials and Methods: Maximum voluntary MBF, IBF, and morphological variables were recorded in 120 subjects (60 males and 60 females) with skeletal class I pattern in the age range of 14 to 24 years. All subjects were divided into 3 groups: Normodivergent, hypodivergent, and hyperdivergent, according to the maxillomandibular plane angle and Jarabak ratio. Bite force measurements were undertaken using a custom-made portable digital gnathodynamometer on the left and the right sides of the jaw in the molar and incisor regions during maximal clenching. Statistical analysis was performed using independent t-test, chi-square test, and ANOVA test using SPSS version 22.0.0.0 software. Results: MBF and IBF are influenced by gender with higher values obtained for male subjects in all groups in the following order: hypodivergent > normodivergent > hyperdivergent. No significant changes were seen with morphological variables in different groups. Conclusion: Molar and incisor biting forces are highest in hypodivergent subjects and least in hyperdivergent subjects as a reflection of jaw morphology and muscular efficiency. In all groups, males exhibit higher force values than females, underlining a strong gender influence on biting force and facial pattern.

Altered muscle activation in agility dogs performing warm-up exercises: an acoustic myography study

Agility is physically demanding and dogs encounter a considerable risk of injury during training and competition. Pre-performance warm-up is used routinely among human athletes to prepare the tissues for these physical demands, but in canine sports evidence for effects of warm-up is lacking. The aim of this study was to investigate the effects of warm-up in dogs on two major muscles involved in locomotion. It was hypothesised that, after warm-up, the muscles would be used more efficiently (more fibre resting time/total time), recruit fewer fibres (reduced spatial summation) and/or activated with a lower firing frequency (reduced temporal summation). The following factors ‘sex, age, weight, height, training level and agility experience’ were evaluated for their potential impact on muscle function parameters. Fourteen large (≥46 cm at the withers) agility dogs of different breeds and training levels performed a 5 min warm-up program three times, with a 2 min break between the programs for recording purposes. Acoustic myography sensors were attached on the skin over the muscles m. triceps brachii (TB) and m. gluteus superficialis (GS). Recordings of muscle activity were made, while the dogs trotted before warm-up and after each 5 min warm-up program. The dogs used TB more efficiently after 5 min (P<0.05), 10 min (P<0.05) and 15 min (P<0.001) of exercise compared to pre-warm-up values. No changes were found in the activity of GS. For well-trained dogs, TB recruited fewer muscle fibres after 10 and 15 min of warm-up compared to dogs that trained less than 1 h weekly (P<0.03). For dogs with more than 2 years of experience, GS had a lower firing frequency before and after 10 min warm-up compared to dogs with less experience. The results indicate that warm-up alters muscle activation by an increased muscular efficiency. Training level and experience have an influence on muscle function parameters.

External mechanical work in the galloping racehorse.

Horse locomotion is remarkably economical. Here, we measure external mechanical work of the galloping horse and relate it to published measurements of metabolic cost. Seven Thoroughbred horses were galloped (ridden) over force plates, under a racing surface. Twenty-six full strides of force data were recorded and used to calculate the external mechanical work of galloping. The mean sum of decrements of mechanical energy was -876 J (±280 J) per stride and increments were 2163 J (±538 J) per stride as horses were accelerating. Combination with published values for internal work and metabolic costs for galloping yields an apparent muscular efficiency of 37-46% for galloping, which would be reduced by energy storage in leg tendons. Knowledge about external work of galloping provides further insight into the mechanics of galloping from both an evolutionary and performance standpoint.

Impact of Parkinson's disease on the efficiency of masticatory cycles: Electromyographic analysis.

BackgroundThis study evaluated the efficiency of masticatory cycles by means of the linear envelope of the electromyographic signal of the masseter and temporalis muscles in individuals with Parkinson’s disease.Material and MethodsTwenty-four individuals were assigned into two groups: with Parkinson’s disease, average ± SD 66.1 ± 3.3 years (n = 12) and without the disease, average ± SD: 65.8 ± 3.0 years (n = 12). The MyoSystem-I P84 electromyograph was used to analyze the activity of masticatory cycles through the linear envelope integral in habitual mastication of peanuts and raisins and non-habitual mastication of Parafilm M®.ResultsThere was statistically significant difference (P ≤ 0.05) between individuals with Parkinson’s disease and without the disease in non-habitual mastication of Parafilm M®, in the right temporal muscle (P = 0.01); habitual mastication of peanuts, in the right temporal muscle (P = 0.02), left temporal muscle (P = 0.03), and right masseter muscle (P = 0.01); and habitual mastication of raisins in the right temporal muscle (P = 0.001), left temporal muscle (P= 0.001), right masseter muscle (P= 0.001) and left masseter muscle (P= 0.03).ConclusionsThese results suggest that Parkinson’s disease interferes in the electromyographic activity of the masticatory cycles by reducing muscular efficiency. Key words:Parkinson’s Disease, electromyography, masticatory efficiency, masseter muscle, temporal muscle.

Zebra finch (Taeniopygia guttata) shift toward aerodynamically efficient flight kinematics in response to an artificial load.

ABSTRACTWe investigated the effect of an added mass emulating a transmitter on the flight kinematics of zebra finches (Taeniopygia guttata), both to identify proximal effects of loading and to test fundamental questions regarding the intermittent flight of this species. Zebra finch, along with many species of relatively small birds, exhibit flap-bounding, wherein the bird alternates periods of flapping with flexed-wing bounds. Mathematical modeling suggests that flap-bounding is less aerodynamically efficient than continuous flapping, except in limited circumstances. This has prompted the introduction of two major hypotheses for flap-bounding – the ‘fixed-gear’ and ‘cost of muscle activation/deactivation’ hypotheses – based on intrinsic properties of muscle. We equipped zebra finches flying at 10 m s−1 with a transmitter-like load to determine if their response was consistent with the predictions of these hypotheses. Loading caused finches to diverge significantly from their unloaded wingbeat kinematics. Researchers should carefully consider whether these effects impact traits of interest when planning telemetry studies to ensure that tagged individuals can reasonably be considered representative of the overall population. In response to loading, average wingbeat amplitude and angular velocity decreased, inconsistent with the predictions of the fixed-gear hypothesis. If we assume that finches maintained muscular efficiency, the reduction in amplitude is inconsistent with the cost of the muscle activation/deactivation hypothesis. However, we interpret the reduction in wingbeat amplitude and increase in the proportion of time spent flapping as evidence that loaded finches opted to increase their aerodynamic efficiency – a response which is consistent with the latter hypothesis.

The Effect of Foam Rolling for Three Consecutive Days on Muscular Efficiency and Range of Motion

BackgroundFoam rolling (FR) has been shown to alleviate some symptoms of exercise-induced muscle damage and has been suggested to increase range of motion (ROM) without negatively impacting strength. However, it is unclear what neuromuscular effects, if any, mediate these changes.MethodsIn a randomized, crossover design, 16 healthy active males completed 2 min of rest or FR of the knee extensors on three consecutive days. Mechanical properties of vastus lateralis (VL) and rectus femoris (RF) were assessed via Tensiomyography. Knee extension maximal voluntary contraction (MVC) and knee flexion ROM were also assessed, and surface electromyography amplitude (RMS) was recorded during a submaximal isometric contraction (50% of MVC). Measures were performed before and after (0, 15, and 30 min) FR or rest.ResultsMVC was reduced on subsequent days in the rest condition compared to FR (p = 0.002, pη2 = 0.04); ROM was not different across time or condition (p = 0.193, pη2 = 0.01). Stiffness characteristics of the VL were different on the third day of FR (p = 0.002, pη2 = 0.03). RMS was statistically reduced 0, 15, and 30 min after FR compared to rest (p = 0.006, pη2 = 0.03; p = 0.003, pη2 = 0.04; p = 0.002, pη2 = 0.04).ConclusionsFollowing FR, MVC was elevated compared to rest and RMS was transiently reduced during a submaximal task. Excitation efficiency of the involved muscles may have been enhanced by FR, which protected against the decline in MVC which was observed with rest.

Musical Agency during Physical Exercise Decreases Pain.

Objectives: When physical exercise is systematically coupled to music production, exercisers experience improvements in mood, reductions in perceived effort, and enhanced muscular efficiency. The physiology underlying these positive effects remains unknown. Here we approached the investigation of how such musical agency may stimulate the release of endogenous opioids indirectly with a pain threshold paradigm.Design: In a cross-over design we tested the opioid-hypothesis with an indirect measure, comparing the pain tolerance of 22 participants following exercise with or without musical agency.Method: Physical exercise was coupled to music by integrating weight-training machines with sensors that control music-synthesis in real time. Pain tolerance was measured as withdrawal time in a cold pressor test.Results: On average, participants tolerated cold pain for ~5 s longer following exercise sessions with musical agency. Musical agency explained 25% of the variance in cold pressor test withdrawal times after factoring out individual differences in general pain sensitivity.Conclusions: This result demonstrates a substantial pain reducing effect of musical agency in combination with physical exercise, probably due to stimulation of endogenous opioid mechanisms. This has implications for exercise endurance, both in sports and a multitude of rehabilitative therapies in which physical exercise is effective but painful.

Effect of acute ingestion of β-hydroxybutyrate salts on the response to graded exercise in trained cyclists

Acute ingestion of ketone salts induces nutritional ketosis by elevating β-hydroxybutyrate (βHB), but few studies have examined the metabolic effects of ingestion prior to exercise. Nineteen trained cyclists (12 male, 7 female) undertook graded exercise (8 min each at ∼30%, 40%, 50%, 60%, 70%, and 80% VO2peak) on a cycle ergometer on two occasions separated by either 7 or 14 days. Trials included ingestion of boluses of either (i) plain water (3.8 mL kg body mass−1) (CON) or (ii) βHB salts (0.38 g kg body mass−1) in plain water (3.8 mL kg body mass−1) (KET), at both 60 min and 15 min prior to exercise. During KET, plasma [βHB] increased to 0.33 ± 0.16 mM prior to exercise and 0.44 ± 0.15 mM at the end of exercise (both p < .05). Plasma glucose was 0.44 ± 0.27 mM lower (p < .01) 30 min after ingestion of KET and remained ∼0.2 mM lower throughout exercise compared to CON (p < .001). Respiratory exchange ratio (RER) was higher during KET compared to CON (p < .001) and 0.03–0.04 higher from 30%VO2peak to 60%VO2peak (all p < .05). No differences in plasma lactate, rate of perceived exertion, or gross or delta efficiency were observed between trials. Gastrointestinal symptoms were reported in 13 out of 19 participants during KET. Acute ingestion of βHB salts induces nutritional ketosis and alters the metabolic response to exercise in trained cyclists. Elevated RER during KET may be indicative of increased ketone body oxidation during exercise, but at the plasma βHB concentrations achieved, ingestion of βHB salts does not affect lactate appearance, perceived exertion, or muscular efficiency.

The effects of real and artificial Leg Length Discrepancy on mechanical work and energy cost during the gait

BackgroundThe impacts of Leg Length Discrepancy (LLD) on the kinematic and dynamic parameters of walking have been widely discussed. But little is known on total mechanical work and energy cost. These two variables are more representative of the functional impairment undergone by the LLD patients. AimTo assess the changes of the mechanical work and energy cost of walking in subjects with real LLD and to compare their results with healthy subjects in whom the LLD has been simulated. MethodThe mechanical work and energy cost data of 60 healthy subjects (speed: 4km/h) with artificial LLD induced by soles (2 and 4cm), 20 patients (speed: 3.75±0.5km/h) with real LLD and 20 matched subjects (speed: 3.75±0.5km/h) were collected. Statistical comparisons between the groups were performed using a t-paired test and ANOVA. ResultsPatients with a real LLD showed a significant decrease in mechanical work and energy cost when compared to norms. Patients with real LLD provide a better recovery when compared to subjects with artificial LLD of 2cm, and a decrease of energy cost and higher muscular efficiency (mechanical work/energy cost) when compared to subjects with artificial LLD of 4cm. ConclusionsOur results showed that patients with a real LLD develop compensatory strategies during gait, probably to minimize the displacement of the body center of mass and consequently reduce the amount of energy expenditure useful for their displacement. Moreover, they adopt a better gait strategy compared to the subjects in whom LLD was simulated.

Blood lactate accumulation decreases during the slow component of oxygen uptake without a decrease in muscular efficiency.

Pulmonary oxygen uptake ([Formula: see text]) slowly increases during exercise above the anaerobic threshold, and this increase is called the slow component of [Formula: see text]. The mechanism of the increase in [Formula: see text] is assumed to be due to increasing energy cost associated with increasingly inefficient muscle contraction. We hypothesized that the increase in [Formula: see text] would be accompanied by a constant or increasing rate of accumulation of blood lactate, indicating sustained anaerobic metabolism while [Formula: see text] increased. Ten male subjects performed cycle ergometry for 3, 6, and 9min at a power output representing 60% of the difference between lactate threshold and maximal [Formula: see text] while [Formula: see text] and blood lactate accumulation were measured. Blood lactate accumulation decreased over time, providing the energy equivalent of (mean±SD) 1586±265, 855±287, and 431±392ml of [Formula: see text] during 0-3, 3-6, and 6-9min of exercise, respectively. As duration progressed, [Formula: see text] supplied 86.3±2.0, 93.6±1.9, and 96.8±2.9% of total energy from 0 to 3, 3 to 6, and 6 to 9min, respectively, while anaerobic contribution decreased. There was no change in total energy cost after 3min, except that required by ventilatory muscles for the progressive increase in ventilation. The slow component of [Formula: see text] is accompanied by decreasing anaerobic energy contribution beyond 3min during heavy exercise.

Effects of internal and external focus of attention on woodwind performance.

When playing a wind instrument, should the performer focus attention on his1 breathing, his fingers, the instrument keys, or the sound coming out of the instrument? This practical question of where to direct one's attention during movement activities has received considerable interest from the field of motor learning. Focusing on an object separate from the person (e.g., flute keys) or on the movement outcome (e.g., flute sound) is an external focus of attention (FOA; Wulf, Hos, & Prinz, 1998). Focusing on part of the body (e.g., is an internal FOA. Because FOA has rarely been investigated in musical contexts, this article will begin by reviewing research that studied the effects of FOA in general motor learning contexts. Next, it will examine theoretical explanations for these effects, discuss the few studies of FOA in music contexts, and then test the application of FOA with a basic task in woodwind performance.In 1998, motor learning specialists Wulf et al. (1998) began a significant line of research examining the effect of a learner's FOA while performing general (nonmusical) motor tasks. Their early laboratory studies used a balance apparatus and a ski-simulator. They found college participants performed movements best when focusing their attention externally rather than internally or when in a no-direction control group. What was particularly interesting about this study was that very slight differences in where participants actually put their attention still caused significant differences in the movement outcomes.The FOA construct has been examined in numerous laboratory and applied settings, including basketball, golf, rowing, swimming, kayak paddling, and dart throwing (for reviews, see Peh, Chow, & Davids, 2011; Wulf, 2013). Results of these investigations almost always show an external FOA led to better performance than an internal FOA (for an exception, see Poolton, Maxwell, Masters, & Raab, 2006). However, it should be noted that the motor tasks used in these studies are predominantly gross motor skills. In one list of studies reviewed by Wulf (2013), 53 studies used gross motor skills, whereas only one study was conducted by music researchers, using a fine motor skill (Duke, Cash, & Allen, 2011). Therefore, although there is considerable evidence supporting the benefits of an external FOA for gross motor skills, it is premature to generalize these findings to the fine motor skills frequently involved in instrumental musical performance.In addition to behavioral outcomes like increased accuracy when putting a golf ball, another way to evaluate the effects of internal and external FOAs is to measure muscular efficiency. Generally, when less energy is expended to produce a specified outcome, this indicates a more efficient movement (Wulf, 2013). Several FOA studies have included electromyography (EMG) to measure differences in muscle activity when participants adopted internal and external FOAs.During bicep curls (Vance, Wulf, Tollner, McNevin, & Mercer, 2004), leg extension/flexion (Kal, van der Kamp, & Houdijk, 2013), basketball free-throws (Zachry, Wulf, Mercer, & Bezodis, 2005), generating force with the foot (Lohse & Sherwood, 2012), and making a vertical jump (Wulf, Dufek, Lozano, & Pettigrew, 2010), an external FOA induced less muscle activity without compromising the outcome measure. In addition, Wulf et al. (2010) demonstrated coordination did not change as a result of FOA conditions while vertical jumping, and the internal FOA caused increased activity in muscles that were not necessary for the movement (Zachry et al., 2005).Neuroscientists have used fMRI to examine the neural correlates of FOA (Zentgraf et al., 2009; Zimmermann et al., 2012). One data collection protocol generated the data for these two publications. University students were trained to use either an internal (concentrate on your moving fingers) or external (concentrate on the keys that need to be pressed) FOA for a button pressing sequence. …

The mechanistic bases of the power-time relationship: muscle metabolic responses and relationships to muscle fibre type.

The power-asymptote (critical power; CP) of the hyperbolic power-time relationship for high-intensity exercise defines a threshold between steady-state and non-steady-state exercise intensities and the curvature constant (W') indicates a fixed capacity for work >CP that is related to a loss of muscular efficiency. The present study reports novel evidence on the muscle metabolic underpinnings of CP and W' during whole-body exercise and their relationships to muscle fibre type. We show that the W' is not correlated with muscle fibre type distribution and that it represents an elevated energy contribution from both oxidative and glycolytic/glycogenolytic metabolism. We show that there is a positive correlation between CP and highly oxidative type I muscle fibres and that muscle metabolic steady-state is attainable <CP but not >CP. Our findings indicate a mechanistic link between the bioenergetic characteristics of muscle fibre types and the power-time relationship for high-intensity exercise. We hypothesized that: (1) the critical power (CP) will represent a boundary separating steady-state from non-steady-state muscle metabolic responses during whole-body exercise and (2) that the CP and the curvature constant (W') of the power-time relationship for high-intensity exercise will be correlated with type I and type IIx muscle fibre distributions, respectively. Four men and four women performed a 3min all-out cycling test for the estimation of CP and constant work rate (CWR) tests slightly >CP until exhaustion (Tlim ), slightly <CP for 24min and until the >CP Tlim isotime to test the first hypothesis. Eleven men performed 3min all-out tests and donated muscle biopsies to test the second hypothesis. Below CP, muscle [PCr] [42.6±7.1vs. 49.4±6.9mmol(kgd.w.)(-1) ], [La(-) ] [34.8±12.6vs. 35.5±13.2mmol(kgd.w.)(-1) ] and pH (7.11±0.08 vs. 7.10±0.11) remained stable between ∼12 and 24min (P>0.05 for all), whereas these variables changed with time >CP such that they were greater [[La(-) ] 95.6±14.1mmol(kgd.w.)(-1) ] and lower [[PCr] 24.2±3.9mmol(kgd.w.)(-1) ; pH 6.84±0.06] (P<0.05) at Tlim (740±186s) than during the <CP trial. The CP (234±53W) was correlated with muscle type I (r=0.67, P=0.025) and inversely correlated with muscle type IIx fibre proportion (r=-0.76, P=0.01). There was no relationship between W' (19.4±6.3kJ) and muscle fibre type. These data indicate a mechanistic link between the bioenergetic characteristics of different muscle fibre types and the power-duration relationship. The CP reflects the bioenergetic characteristics of highly oxidative type I muscle fibres, such that a muscle metabolic steady-state is attainable below and not above CP.

Differences in Oxygen Extraction Compared to Healthy Subjects Contribute to Muscular Efficiency in Cystic Fibrosis

Differences in Oxygen Extraction Compared to Healthy Subjects Contribute to Muscular Efficiency in Cystic Fibrosis